Public health authorities warn of the hazards of too much sun exposure. However, excessive UVR exposure accounts for only 0.1% of the total global burden of disease in disability-adjusted life years (DALYs), according to the 2006 World Health Organization (WHO) report The Global Burden of Disease Due to Ultraviolet Radiation. In contrast, the same WHO report noted that a markedly larger annual disease burden of 3.3 billion DALYs worldwide might result from very low levels of UVR exposure. This burden subsumes major disorders of the musculoskeletal system and possibly an increased risk of various autoimmune diseases and life-threatening cancers.
What are the benefits that exposure to natural sunlight provide?
Sunlight and Cancer
The connection between vitamin D deficiency and cancer was first made by Drs. Frank and Cedric Garland from the University of California, San Diego. After finding that the incidence of colon cancer was nearly three times higher in New York than in New Mexico, the Garland brothers hypothesized that lack of sun exposure, resulting in a Vitamin D deficiency, played a role. Research now indicates that being deficient in vitamin D increases the risk of many cancers, especially breast and colon. For example, a four-year, placebo-controlled study involving 1,179 postmenopausal women concluded that vitamin D supplementation produced a dramatic 60% drop in the risk of developing any form of cancer. Another study published in the September 2008 "Clinical Journal of the American Society of Nephrology" noted a reported 30- to 50-percent reduction in the risk of certain cancers with an increase in sun exposure.
Sunlight and psoriasis.
Exposure to sunlight is extremely beneficial for individuals with psoriasis. In one study, an outdoor four-week sunbathing therapy was shown to promote significant clearance of psoriatic symptoms in 84 percent of subjects. "The sun is one of the best treatments for psoriasis, so in summer I encourage my patients to sit out on the deck and give their affected areas a good sun bath," said Julie Moore, M.D., dermatologist at Gottlieb Memorial Hospital. "30 minutes is adequate to improve the skin; you do not need to sit out for hours." The ultraviolet rays in the sun are beneficial to the irritated skin.
Sunlight and Mood
During periods without sunshine, many people suffer from depression. It's called seasonal affective disorder (SAD). Besides feeling gloomy, people experiences low energy. Scientific research has examined the frequently observed relationship between sunlight and mood. A study from Denmark, published in the September 2011 issue of the "Scandinavian Journal of Work, Environment and Health," demonstrated that outdoor work, even in the winter, provided enough sunlight to counteract mood difficulties. Researchers found that regardless of the season, the turnover of serotonin in the brain was affected by the amount of sunlight on any given day. And the levels of serotonin were higher on bright days than on overcast or cloudy ones. In fact, the rate of serotonin production in the brain was directly related to the duration of bright sunlight.
Sunlight and Heart Health
Exposure to sunlight has a beneficial impact on blood pressure and heart health. A study published in the March 2010 "European Heart Journal" showed that the beneficial effects of sunlight on heart health and blood pressure may be related to the chemical nitric oxide, which acts on blood vessels to decrease blood pressure. Nitric oxide activity may be modulated by sunlight. The immediate effects on the heart and blood pressure appear to be short-term, lasting less than 24 hours without additional sunlight exposure.
New research conducted by the Universities of Southampton and Edinburgh in the UK, and published in the Journal of Investigative Dermatology, suggests that exposure to sunlight may help reduce blood pressure. In turn, this could cut the risk of heart attack and stroke.
Sunlight and Multiple Sclerosis
Its well-known that sunlight and Vitamin D are beneficial to those with Multiple Sclerosis. However, new evidence has come to light that at least some of sunlights apparent ability to protect against MS does not come from vitamin D.
A study published in the Proceedings of the National Academy of Sciences in March 2010 used an animal model of MS known as experimental autoimmune encephalomyelitis (EAE). In this study, laboratory animals with MS were exposed to ultraviolet (UV) light, which led to dramatic reductions in the activity of the disease. However, the UV light only brought about a small and transient rise in vitamin D levels in the animals. The magnitude and duration of this rise would be insufficient to account for the considerable benefit conferred by UV light.The authors of this study concluded, These results suggest that UVR [ultraviolet radiation] is likely suppressing disease independent of vitamin D production and that vitamin D supplementation alone may not replace the ability of sunlight to reduce MS susceptibility.
Sunlight and Cholesterol
Sunlight lowers cholesterol. The sun converts high cholesterol in the blood into steroid hormones and the sex hormones we need for reproduction. In the absence of sunlight, the opposite happens; substances convert to cholesterol.